1. Field of the Invention (Technical Field)
The present invention relates to methods of fault testing analog, digital, and hybrid integrated circuits, and apparatuses therefor.
2. Background Art
The complexity of integrated circuit testing is rapidly increasing due to the more prevalent use of mixed-mode (digital-analog) circuits and the smaller feature size of current fabrication processes. It is becoming evident that traditional test techniques are no longer adequate for detecting the presence of faults in these circuits.
The current technique for making fabrication defects observable is through the use of steady-state rail current measurements (IDDQ). This technique allows some reduction of the number of test vectors, but is only appropriate for circuits with zero or very small quiescent currents like CMOS digital circuits and class AB analog circuits.
Hashizume, et al., "Fault Detection of Combinational Circuits Based on Supply Current", 1988 International Test Conference, ch. 26104/88, pp. 374-379, addressed the issue of analyzing spectral content of IDD current under normal and faulty operation. Hashizume, et al., did present a method for fault detection based on detecting changes in power supply currents using pattern recognition techniques, but this method requires specific test vectors for making the faults observable.
J. Frenzel and P. Marinos, "Power Supply Current Signature (PSCS) Analysis: A New Approach to System Testing," 1987 International Test Conference, ch. 23472/87, pp. 125-135, also discloses a test-vector dependent method. Dorey, et al., Rapid Reliability Assessment of VLSICs, New York and London: Plenum Press, 1990, is also test-vector dependent.
U.S. Pat. No. 5,057,774, to Verhelst, et al., entitled "Apparatus for Measuring the Quiescent Current of an Integrated Monolithic Digital Circuit", tests only digital IC's and only measures steady state quiescent current.
U.S. Pat. No. 4,710,704, to Ando, entitled "IC Test Equipment", likewise does not employ instantaneous rail current as a test vector. Similarly for U.S. Pat. No. 4,631,724, to Shimizu, entitled "Semiconductor Memory Test Equipment", which only tests CMOS memory devices.
U.S. Pat. No. 4,630,228, to Tarczy-Hornoch, et al., entitled "Transmission Line Analyzer for Automatically Identifying the Severities and Location of Multiple Mismatches", employs a fast Fourier transform algorithm for analyzing transmission line mismatches--not integrated circuits. Likewise, U.S. Pat. No. 3,803,484, to Gray, entitled "Method and Apparatus for Measuring Deterioration in a Shielded Cable by High Frequency Pulse Injection", detects only cable deterioration.
The prior art lacks a VLSIC (Very Large Scale Integrated Circuit) test method wherein the power supply rails are pulsed while a common DC bias voltage is applied to all inputs. In other words, the prior art lacks a test vector-independent method equally applicable to digital and analog integrated circuits.